如何在 increasing/decreasing 后将 int 的值重置为 0

Question

在开始之前我想说我只是一个初学者所以我希望你能理解我为什么要问这么简单的问题:)

使用“+”和“-”按钮，我调整了数量。然后使用 "order" 按钮，显示价格。但是当我按下"restart"按钮，然后再次调整数量时，数量不会从0开始，而是从最新的数量开始。

这是XML:

<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_margin="16dp"
    android:textSize="16sp"
    android:textAllCaps="true"
    android:text="Quantity"
    android:id="@+id/quantity" />

<Button
    android:layout_width="48dp"
    android:layout_height="48dp"
    android:layout_marginLeft="16dp"
    android:layout_marginBottom="16dp"
    android:layout_below= "@id/quantity"
    android:text="+"
    android:id="@+id/increment"
    android:onClick="increment" />

<TextView
    android:layout_width="48dp"
    android:layout_height="48dp"
    android:layout_marginLeft="16dp"
    android:layout_marginBottom="16dp"
    android:layout_below= "@id/quantity"
    android:layout_toRightOf = "@id/increment"
    android:textSize="16sp"
    android:textColor="#000000"
    android:gravity="center"
    android:text="0"
    android:id="@+id/quantity_text_view" />

<Button
    android:layout_width="48dp"
    android:layout_height="48dp"
    android:layout_marginLeft="16dp"
    android:layout_marginBottom="16dp"
    android:layout_below= "@id/quantity"
    android:layout_toRightOf= "@id/quantity_text_view"
    android:text="-"
    android:id="@+id/decrement"
    android:onClick="decrement" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginLeft="16dp"
    android:layout_marginBottom="16dp"
    android:layout_below= "@id/increment"
    android:textSize="16sp"
    android:textAllCaps="true"
    android:text="Price"
    android:id="@+id/price" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginLeft="16dp"
    android:layout_marginBottom="16dp"
    android:layout_below= "@id/price"
    android:textSize="16sp"
    android:textColor="#000000"
    android:text="[=11=].00"
    android:id="@+id/price_text_view" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginLeft="16dp"
    android:layout_marginBottom="16dp"
    android:layout_below= "@id/price_text_view"
    android:text="Order"
    android:id="@+id/button"
    android:onClick="submitOrder" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below= "@id/button"
    android:textSize="16sp"
    android:text=""
    android:id="@+id/enjoy" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginRight="16dp"
    android:layout_marginBottom="16dp"
    android:layout_alignParentBottom="true"
    android:layout_alignParentRight="true"
    android:text="Restart"
    android:id="@+id/restart"
    android:onClick="restart" />

</RelativeLayout>

这里是 Java:

public class MainActivity extends ActionBarActivity {

int quantity = 0;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    final Button button = (Button) findViewById(R.id.button);
    button.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            TextView view = (TextView) findViewById(R.id.enjoy);
            view.setPadding(16, 0, 0, 16);
            view.setText("Enjoy!");
            displayPrice(quantity * 5);
        }
    });
}

/**
 * This method is called when the + button is clicked.
 */
public void increment(View view){
    quantity = quantity + 1;
    display(quantity);
}

/**
 * This method is called when the - button is clicked.
 */
public void decrement(View view){
    quantity = quantity - 1;
    display(quantity);
}

/**
 * This method is called when the order button is clicked.
 */
public void submitOrder(View view) {
    display(quantity);

}

/**
 * This method displays the given quantity value on the screen.
 */
private void display(int number) {
    TextView quantityTextView = (TextView) findViewById(
            R.id.quantity_text_view);
            quantityTextView.setText("" + number);
}

/**
 * This method displays the given price on the screen.
 */
private void displayPrice(int number) {
    TextView priceTextView = (TextView) findViewById(R.id.price_text_view);
    priceTextView.setText(NumberFormat.getCurrencyInstance().format(number));
}

public void restart(View v) {
    int quantity = 0;
    display(quantity);
    displayPrice(quantity);
    TextView view = (TextView) findViewById(R.id.enjoy);
    view.setPadding(0, 0, 0, 0);
    view.setText("");
}
}

我想实现的是在按下重启按钮后，intquantity的值会重置为0

Answer 1

在您的重启方法中，您正在创建一个名为 quantity 的新变量；但是，您应该使用已经为 class 定义的数量。只需将方法更改为：

public void restart(View v) {
    quantity = 0;
    display(quantity);
    displayPrice(quantity);
    TextView view = (TextView) findViewById(R.id.enjoy);
    view.setPadding(0, 0, 0, 0);
    view.setText("");
}

Answer 2

变量范围很重要。您在重启方法中声明了一个新变量，而不是使用您已经在 MainActivity 中声明的变量。

public void restart(View v) {
     quantity = 0;
     display(quantity);
     displayPrice(quantity);
     TextView view = (TextView) findViewById(R.id.enjoy);
     view.setPadding(0, 0, 0, 0);
     view.setText("");
}

如何在 increasing/decreasing 后将 int 的值重置为 0

How do I reset the value of an int to 0 after increasing/decreasing it´s value

java

xml

int

android